Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
  • H01G11/54—Electrolytes
  • H01G11/58—Liquid electrolytes
  • H01G11/60—Liquid electrolytes characterised by the solvent
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
  • H01G11/54—Electrolytes
  • H01G11/58—Liquid electrolytes
  • H01G11/62—Liquid electrolytes characterised by the solute, e.g. salts, anions or cations therein
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
  • H01G9/004—Details
  • H01G9/022—Electrolytes; Absorbents
  • H01G9/035—Liquid electrolytes, e.g. impregnating materials
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
  • H01M10/0566—Liquid materials
  • H01M10/0568—Liquid materials characterised by the solutes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M2300/00—Electrolytes
  • H01M2300/0017—Non-aqueous electrolytes
  • H01M2300/0025—Organic electrolyte
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/13—Energy storage using capacitors
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/60—Other road transportation technologies with climate change mitigation effect
  • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Definitions

• Energy storage devices such as ultracapacitors may be used in many applications where a discrete power pulse is required. Such applications range from cell phones to hybrid vehicles.
• An important characteristic of an ultracapacitor is the energy density that it can provide.
• the energy density of the device which can comprise two or more carbon-based electrodes separated by a porous separator and/or an organic electrolyte, is largely determined by the properties of the electrolyte.
• TEA-TFB One factor that is important in the development of electrolyte solutions is cost. Due to its relatively expensive synthesis and purification, commercially-available TEA-TFB is expensive. An example synthesis of TEA-TFB is disclosed in U.S. Patent No. 5,705,696. The example process involves reacting tetraalkyl ammonium halides with metal
• a method of forming an electrolyte solution comprises combining ammonium tetrafluoroborate and a quaternary ammonium halide salt in a liquid solvent to form a quaternary ammonium tetrafluoroborate and an ammonium halide, and removing the ammonium halide from the solvent to form an electrolyte solution.
• the reaction can be carried out entirely at about room temperature.
• the filtration step may be carried out at temperatures below room temperature.
• filtration at a temperature below room temperature produces lower bromide ion content.
• a stoichiometric excess of ammonium tetrafluoroborate can be used to minimize the concentration of halide ions in the product.
• the resulting product is an electrolyte solution comprising a quaternary ammonium tetrafluoroborate salt dissolved in a solvent, wherein a concentration of chloride ions in the electrolyte solution is less than 1 ppm, a concentration of bromide ions in the electrolyte solution is less than 1000 ppm, less than 500 ppm, less than 200 ppm, less than 100 ppm, less than 80 ppm or less than 50 ppm, and a concentration of ammonium ions in the electrolyte solution is greater than 1 ppm.
• FIG. 1 is a schematic illustration of a button cell according to one embodiment
• Fig. 2 is CV curve for an electrolyte solution prepared using a stoichiometric ratio of reactants; and [0012] Fig. 3 is a CV curve for an electrolyte solution prepared using a stoichiometric excess of ammonium tetrafluoroborate.
• a method of making quaternary ammonium tetrafluoroborate involves reacting one or more quaternary ammonium halides with ammonium tetrafluoroborate in an organic solvent.
• the reaction products are quaternary ammonium tetraflurorborate and ammonium bromide.
• the quaternary ammonium tetraflurorborate is soluble in the organic solvent, while the ammonium bromide forms as a precipitate.
• the precipitated NH 4 Br can be filtered to form a solution of, for example, TEA-TFB in an organic solvent such as acetonitrile.
• the complete reaction is carried out at about room temperature under constant agitation.
• the reaction is carried out at about room temperature under constant agitation, and then the filtration step is carried out at a temperature below room temperature.
• below room temperature comprises a temperature that corresponds to the lowest possible temperature where the electrolyte salt will not precipitate.
• below room temperature comprises a temperature that corresponds to the temperature where the bromide ions are minimized.
• below room temperature comprises a temperature that corresponds to the lowest possible temperature where the electrolyte salt will not precipitate and bromide ions are minimized.
• below room temperature comprises a temperature that maximizes the difference in solubility parameters for the electrolyte salt and impurities.
• below room temperature comprises from about 20 to about -30°C, from about 15 to about -30°C, from about 10 to about -30°C, from about 5 to about -30°C, from about 0 to about -30°C, from about -5 to about -30°C, from about -10 to about -30°C, from about -15 to about -30°C, from about -20 to about -30°C, from about -25 to about -30°C, from about 20 to about -25°C, from about 15 to about -25°C, from about 10 to about -25°C, from about 5 to about -25°C, from about 0 to about -25°C, from about -5 to about -25°C, from about -10 to about -25°C, from about -15 to about -25°C, from about -20 to about -25°C, from about 20 to about -20°C, from about 15 to about -20°C, from about 10 to about -20°C, from about 5 to about -20°C, from about -20°C, from about
• Suitable quaternary ammonium halides include tetramethyl ammonium
• example organic solvents include dipolar aprotic solvents such as propylene carbonate, butylene carbonate, ⁇ -butyrolactone, acetonitrile, propionitrile, and methoxyacetonitrile.
• dipolar aprotic solvents such as propylene carbonate, butylene carbonate, ⁇ -butyrolactone, acetonitrile, propionitrile, and methoxyacetonitrile.
• a quaternary ammonium halide can be combined with a stoichiometric excess of ammonium tetrafluoroborate.
• the electrolyte solution can be formed using a stoichiometric amount of ammonium tetrafluoroborate, or by using up to 150% (by mole) excess ammonium tetrafluoroborate.
• a molar ratio of quaternary ammonium halide to ammonium tetrafluoroborate can range from 1 : 1 to 1 : 1.5 (e.g., 1 : 1, 1 : 1.1, 1 : 1.2, 1 : 1.3, 1 : 1.4 or 1 : 1.5).
• the resulting solution can include an excess of BF 4 and NH 4 ions.
• Excess ammonium ions from the ammonium tetrafluoroborate can beneficially scavenge halide ions during the synthesis.
• Halide ions can also contribute to unwanted Faradaic reactions in the resulting electrolyte.
• An electrolyte solution comprises a quaternary ammonium tetrafluoroborate salt dissolved in a solvent, wherein a concentration of chloride ions in the electrolyte solution is less than 1 ppm, a concentration of bromide ions in the electrolyte solution is less than 1000 ppm, less than 500 ppm, less than 200 ppm, less than 100 ppm, less than 80 ppm or less than 50 ppm; and a concentration of ammonium ions in the electrolyte solution is grater than 1 ppm.
• a conductivity of the electrolyte solution at 25°C can be at least 45 mS/cm (e.g., at least 45, 50, 55 or 60 mS/cm).
• a total concentration of the quaternary ammonium tetrafluoroborate salt in the electrolyte solution can range from 0.1M to 2M (e.g., 0.1, 0.2, 0.5, 1, 1.5 or 2M).
• Electrolyte solutions according to an embodiment of the present invention show excellent performance in ultracapacitors.
• electrolytic cells utilizing solutions of an embodiment show performance of less than 20% capacitance fade at 65°C and 2.5 V.
• the electrolyte solution can be incorporated into an ultracapacitor.
• a pair of electrodes is separated by a porous separator and the electro de/separator/electrode stack is infiltrated with the electrolyte solution.
• the electrodes may comprise activated carbon that has optionally been mixed with other additives.
• the electrodes can be formed by compacting the electrode raw materials into a thin sheet that is laminated to a current collector via an optional conductive adhesion layer and an optional fused carbon layer.
• the disclosed electrolytes can also be incorporated into other electrochemical electro de/device structures such as batteries or fuel cells.
• activated carbon examples include coconut shell-based activated carbon, petroleum coke-based activated carbon, pitch-based activated carbon, polyvinylidene chloride-based activated carbon, polyacene-based activated carbon, phenolic resin-based activated carbon, polyacrylonitrile-based activated carbon, and activated carbon from natural sources such as coal, charcoal or other natural organic sources.
• Suitable porous or activated carbon materials are disclosed in commonly-owned U.S. Patent Application Nos. 12/970,028 and 12/970,073, the entire contents of which are incorporated herein by reference.
• Activated carbon can be characterized by a high surface area.
• High surface area electrodes can enable high energy density devices.
• high surface area activated carbon is meant an activated carbon having a surface area of at least 100 m 2 /g (e.g., at least 100, 500, 1000 or 1500 m 2 /g).
• the electrodes used to form an ultracapacitor can be configured identically or differently from one another.
• at least one electrode comprises activated carbon.
• An electrode that includes a majority by weight of activated carbon is referred to herein as an activated carbon electrode.
• an activated carbon electrode includes greater that about 50 wt.% activated carbon (e.g., at least 50, 60, 70, 80, 90 or 95 wt.% activated carbon).
• the activated carbon comprises pores having a size of ⁇ 1 nm, which provide a combined pore volume of > 0.3 cm 3 /g; pores having a size of from > 1 nm to ⁇ 2 nm, which provide a combined pore volume of > 0.05 cffiVg; and ⁇ 0.15 cm 3 /g combined pore volume of any pores having a size of > 2 nm.
• Electrodes can include one or more binders. Binders can function to provide mechanical stability to an electrode by promoting cohesion in loosely assembled particulate materials. Binders can include polymers, co-polymers, or similar high molecular weight substances capable of binding the activated carbon (and other optional components) together to form porous structures.
• binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride, or other fluoropolymer particles; thermoplastic resins such as polypropylene, polyethylene, or others; rubber-based binders such as styrene-butadiene rubber (SBR); and combinations thereof.
• PTFE can be utilized as a binder.
• fibrillated PTFE can be utilized as a binder.
• an electrode can include up to about 20 wt% of binder (e.g., up to about 5, 10, 15, or 20 wt%).
• An electrode can also include one or more conductivity promoters.
• a conductivity promoter functions to increase the overall conductivity of the electrode.
• Exemplary conductivity promoters include carbon black, natural graphite, artificial graphite, graphitic carbon, carbon nanotubes or nanowires, metal fibers or nanowires, graphenes, and
• an electrode can include up to about 10 wt% of a conductivity promoter.
• an electrode can include from about 1 wt% to about 10 wt% of conductivity promoter (e.g., 1, 2, 4, or 10 wt %).
• Example ultracapacitors can include one activated carbon electrode or two activated carbon electrodes.
• one electrode can include a majority of activated carbon and the other electrode can include a majority of graphite.
• the electrolyte solution can be characterized by measurements performed on the electrolyte solution itself, as well as by measurements performed on test cells that incorporate the electrolyte solution.
• FIG. 1 An embodiment of an EDLC, a button cell, is shown in Figure 1.
• the button cell 10 includes two current collectors 12, two sealing members 14, two electrodes 16, a separator 18, and an electrolyte solution 20.
• Two electrodes 16, each having a sealing member 14 disposed around the periphery of the electrode, are disposed such that the electrode 16 maintains contact with a current collector 12.
• a separator 18 is disposed between the two electrodes 16.
• An electrolyte solution 20 is contained between the two sealing members.
• An activated carbon-based electrode having a thickness in the range of about 50- 300 micrometers can be prepared by rolling and pressing a powder mixture comprising 80-90 wt.% microporous activated carbon, 0-10 wt.% carbon black and 5-20 wt.% binder (e.g., a fluorocarbon binder such as PTFE or PVDF).
• a liquid can be used to form the powder mixture into a paste that can be pressed into a sheet and dried.
• Activated carbon- containing sheets can be calendared, stamped or otherwise patterned and laminated to a conductive adhesion layer to form an electrode.
• the button cells were fabricated using activated carbon electrodes
• the activated carbon electrodes were fabricated by first mixing activated carbon with carbon black in an 85:5 ratio.
• PTFE was added to make a 85:5: 10 ratio of carbonxarbon black:PTFE.
• the powder mixture was added to isopropyl alcohol, mixed, and then dried.
• the dried material was pressed into a 10 mil thick pre-form.
• the pre-forms were then laminated over a conductive adhesion layer (50 wt.% graphite, 50 wt.% carbon black), which was formed over a fused carbon-coated current collector.
• the current collectors were formed from platinum foil, and the separator was formed from cellulose paper. Prior to assembly, the activated carbon electrodes and the separator were soaked in an electrolyte. A thermoset polymer ring is formed around the periphery of the assembly to seal the cell, which is filled with an organic electrolyte such as tetraethylammonium-tetrafluoroborate (TEA-TFB) in acetonitrile. Prior to sealing the cell, an extra drop of the electrolyte was added to the cell.
• TEA-TFB tetraethylammonium-tetrafluoroborate
• Electrochemical experiments were used to test the cell, included cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge. Cyclic voltammetry experiments were performed at a scan rate of 20 mV/sec within various potential windows over the maximum range of 0 to 4.5 V. The EIS test included measuring impedance while applying an AC perturbation with an amplitude of 10 mV at a constant DC voltage of 0 V over the frequency range of 0.01-10,000 Hz. Galvanostatic charge / discharge experiments were performed at a current magnitude of 10mA.
• CV cyclic voltammetry
• EIS electrochemical impedance spectroscopy
• galvanostatic charge/discharge were performed at a scan rate of 20 mV/sec within various potential windows over the maximum range of 0 to 4.5 V.
• the EIS test included measuring impedance while applying an AC perturbation with an amplitude of 10 mV at a constant DC voltage of 0 V over the
• the energy density of the device was calculated using the Integrated Energy Method.
• the galvanostatic data (potential vs. time data) was numerically integrated and multiplied by the discharge current to obtain the energy delivered by the device (in Ws) between two potentials Vi and V 2 .
• the device capacitance (Cdevice in Farads) can be calculated from the energy according to the following relationship:
• the stable voltage which is the maximum voltage the device can withstand without appreciable Faradaic reactions, was measured from a series of cyclic voltammetry (CV) experiments performed over several different voltage windows. From the CV data, a Faradaic Fraction was measured using the following equation:
• the charge (Q) during anodic and cathodic scans was calculated by integrating the CV curve and dividing the result by the scan rate at which the CV was performed.
• the stable voltage was defined as the potential at which the Faradaic Fraction is approximately 0.1.
• the suspension was filtered to remove the precipitate.
• the conductivity of the electrolyte solution was 64 mS/cm.
• the resulting electrolyte solution was incorporated into a button cell as described above using activated carbon having a surface area of 1800 m 2 /g.
• the energy density of the button cell was 17 Wh/1.
• the CV curve showed no Faradaic reactions.
• the bromide ion content in the electrolyte solution determined by ion chromatography data was 751 ppm.
• the chloride ion content was less than 0.05 ppm, and concentration of ammonium ions was 245 ppm.
• a step-wise addition of reactants means that at least one (preferably both) of the reactants is introduced to the mixture both before and after the introduction of the other reactant.
• a step-wise addition of reactants A and B can include the introduction of the reactants in the following example sequences: ABA, BAB, ABAB, BABA, ABABA, BABAB, etc.
• An electrolyte solution was prepared by adding 200 ml of high purity acetonitrile to a 500 ml Erlenmeyer flask. Tetraethyl ammonium bromide (63 g) was added slowly while stirring. To this solution 33.4 grams of ammonium tetrafluoroborate was slowly added. The flask was sealed to prevent losses of acetonitrile during the mixing process and temperature was maintained at 22-23°C.
• the reaction mixture was allowed to mix thoroughly for 24 hours to complete the reaction.
• the solution with the ammonium bromide by-product was then filtered at room temperature.
• the resulting electrolyte was measured using an Electron- Spray IC/MS instrument by Gentech Scientific system to determine the relative bromide ion concentration with reference to BF 4 ion in the electrolyte solution.
• the electrolyte obtained via room temperature filtration showed bromide ion concentrations of 100-150 ppm.
• An electrolyte solution was prepared as in Example 4, except that the filtration was carried out at -5°C.
• the solution was cooled using a Brookfield Model TC 202 chiller and kept at -5°C for 45 minutes prior to filtration.
• the resulting chilled solution was filtered using an Ertel Alsop pressure filtration system.
• the resulting electrolyte was measured using an Electron-Spray IC/MS instrument by Gentech Scientific system to determine the relative bromide ion concentration with reference to BF 4 ion in the electrolyte solution.
• the electrolyte obtained via low temperature filtration had a bromide content of 50-80 ppm.
• Ranges can be expressed herein as from “about” one particular value, and/or to "about” another particular value. When such a range is expressed, examples include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
• each of the combinations A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are specifically contemplated and should be considered disclosed from disclosure of A, B, and C; D, E, and F; and the example combination A-D.
• any subset or combination of these is also specifically contemplated and disclosed.
• the sub-group of A-E, B- F, and C-E are specifically contemplated and should be considered disclosed from disclosure of A, B, and C; D, E, and F; and the example combination A-D.
• This concept applies to all aspects of this disclosure including, but not limited to any components of the compositions and steps in methods of making and using the disclosed compositions.
• each of these additional steps can be performed with any specific embodiment or combination of embodiments of the disclosed methods, and that each such combination is specifically contemplated and should be considered disclosed
• references herein refer to a component of the present invention being “configured” or “adapted to” function in a particular way.
• a component is “configured” or “adapted to” embody a particular property, or function in a particular manner, where such recitations are structural recitations as opposed to recitations of intended use.
• the references herein to the manner in which a component is “configured” or “adapted to” denotes an existing physical condition of the component and, as such, is to be taken as a definite recitation of the structural characteristics of the component.

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